Background: It has been reported that pumping a shunt in situ may precipitate a proximal occlusion, and/or lead to ventricular over-drainage, particularly in the context of small ventricles. In the laboratory we measured the effect of pumping the pre-chamber of hydrocephalus shunts on intracranial hypotension.

Materials and methods: A simple physical model of the CSF space in a hydrocephalic patient was constructed with appropriate compliance, CSF production and circulation. This was used to test eleven different hydrocephalus shunts. The lowest pressure obtained, the number of pumps needed to reach this pressure, and the maximum pressure change with a single pump, were recorded.

Conclusion: Patients, carers and professionals should be warned that 'pumping' a shunt's pre-chamber may cause a large change in intracranial pressure and predispose the patient to ventricular catheter obstruction or other complications.

Figure 3: Single test of the PS Medical Lumboperitoneal Reservoir using the model of human CSF space. Pumping started at the vertical bar. Pressure decreased slowly at first on the plateau (Fig. 2b- high-compliance section of the pressure-volume curve) and then started to accelerate (on the steep, low-compliance section of pressure-volume curve), and then it reached the asymptote. Arrow indicates the region where pressure changes are greatest per one pump and these values are taken for comparison between valves (see Fig 6).

Mentions:
For all valves, the negative pressure in the model mimicking the intracranial pressure (ICP) at which an asymptote occurs, was determined by pumping the shunt reservoir continuously, at a constant rate of 1s-1, until the asymptote was reached (Fig. 3). The PS Medical Lumboperitoneal shunt had the largest reservoir and could only be pumped at a rate of 1 stroke per 3s, due to the longer refill time. The negative pressure achieved was measured from the data recorded in BioSAn for Win95 [16].

Figure 3: Single test of the PS Medical Lumboperitoneal Reservoir using the model of human CSF space. Pumping started at the vertical bar. Pressure decreased slowly at first on the plateau (Fig. 2b- high-compliance section of the pressure-volume curve) and then started to accelerate (on the steep, low-compliance section of pressure-volume curve), and then it reached the asymptote. Arrow indicates the region where pressure changes are greatest per one pump and these values are taken for comparison between valves (see Fig 6).

Mentions:
For all valves, the negative pressure in the model mimicking the intracranial pressure (ICP) at which an asymptote occurs, was determined by pumping the shunt reservoir continuously, at a constant rate of 1s-1, until the asymptote was reached (Fig. 3). The PS Medical Lumboperitoneal shunt had the largest reservoir and could only be pumped at a rate of 1 stroke per 3s, due to the longer refill time. The negative pressure achieved was measured from the data recorded in BioSAn for Win95 [16].

Background: It has been reported that pumping a shunt in situ may precipitate a proximal occlusion, and/or lead to ventricular over-drainage, particularly in the context of small ventricles. In the laboratory we measured the effect of pumping the pre-chamber of hydrocephalus shunts on intracranial hypotension.

Materials and methods: A simple physical model of the CSF space in a hydrocephalic patient was constructed with appropriate compliance, CSF production and circulation. This was used to test eleven different hydrocephalus shunts. The lowest pressure obtained, the number of pumps needed to reach this pressure, and the maximum pressure change with a single pump, were recorded.

Conclusion: Patients, carers and professionals should be warned that 'pumping' a shunt's pre-chamber may cause a large change in intracranial pressure and predispose the patient to ventricular catheter obstruction or other complications.